map<pair<ll,ll>,map<pair<ll,ll>,ll>>mm;
ll@n,@(x,y)[n],z=0;
rep(i,n){
	rep(j,i){
		ll cx=x[i]+x[j];
		ll cy=y[i]+y[j];
		map<pair<ll,ll>,ll>&m=mm[{cx,cy}];
		ll dx=x[i]-x[j];
		ll dy=y[i]-y[j];
		ll ex;
		ll ey;
		if(dx==0){
			dy=1;
			ex=1;
			ey=0;
		}else if(dy==0){
			dx=1;
			ex=0;
			ey=1;
		}else{
			ll g=gcd(abs(dx),abs(dy));
			dx/=g;
			dy/=g;
			if(dy<0){
				dx=-dx;
				dy=-dy;
			}
			ex=-dy;
			ey=dx;
			if(ey<0){
				ex=-ex;
				ey=-ey;
			}
		}
		m[{dx,dy}]+=1;
		auto t=m.find({ex,ey});
		if(t!=m.end()){
			z+=t->second;
		}
	}
}
wt(z);